Different techniques of capturing spatial data make it possible to create point clouds with various characteristics. Geavis compared point clouds obtained by using two different technologies, i.e.

• 3D terrestrial laser scanning,
• photogrammetric procedures based on aerial photos.

The same test object was used to test and compare both technologies, namely the Church of St. Primus and Felician located in the village of Jamnik above Kropa.

Terrestrial laser scanning was carried out with a robotic LEICA MS60 tachometer from four standing points. The density of measurements was determined by setting a distance of 3 cm between the measured points 50 m from the church, enabling us to obtain four point clouds. Due to the precisely known starting point of the instrument and its orientation, the point clouds were mutually consistent. On surfaces measured from two or more standing points, the difference between the points of the same object detail was not noticeable within individual clouds. The measuring at an individual standing point took about an hour, including the defining of the starting point and orientation of the instrument.

The photogrammetric point cloud was made from 380 aerial photos taken above the church in the course of two flights that took a total of 15 minutes. The average point density in the created point cloud amounted to app. 100 points/m2.

A comparison of both point clouds yielded the following results:

The point cloud obtained through terrestrial laser scanning contains less noise, the points are evenly distributed regardless of the object’s surface texture. The tachometer sensor is active and requires more energy than the unmanned aircraft’s camera. The laser scanning range is limited to a few hundred metres. The capture of spatial data is a lengthy process, while setting up new standing points in order to avoid dead angles is time-consuming and in some cases even impossible.

The point cloud obtained through photogrammetric procedures from aerial photos is denser, but contains more noise which can be partially removed by employing statistical methods due to the high density of the points. The passive sensor of the unmanned aircraft serves as a camera and uses little energy. Spatial data capture – aerial photography – is a quick procedure, enabling speedier and simpler capture of all the object’s details without any dead angles.

Based on the comparison of both types of clouds, Geavis can sum up that, by properly incorporating both technologies, the advantages of both methods can be merged in one product, enabling the client the best possible basis for further modelling and analyses.